In many termite species, for example, soldier castes are highly developed, and colony members never leave their nests of dead wood because, like gall aphids and gall thrips, they are able to feed off the walls.

And after identifying worker ants in several of the fossils, he believes that ants had already begun to specialize into castes.

The new study also reveals how elements in the genome may influence the development of vastly different honeybee castes, such as queens and workers, from the same genetic material.

Origin

The general sense in early use was ‘race, breed’. It is from Spanish and Portuguese casta ‘lineage, race, breed’, feminine of casto ‘pure, unmixed’, from Latin castus ‘chaste’, also the source of castigate (early 17th century), and chasten (mid 16th century) ‘make chaste’, and chaste (Middle English) itself. The common current use is to refer to the hereditary classes of Hindu society: Brahman (priest), Kshatriya (warrior), Vaisya (merchant or farmer), and Sudra (labourer).